I haven't had that particular action apart, but they all have some things in common.
1) Typically there has to be a shoulder on the firing pin which keeps the pin from slamming into the end of the barrel if you dry fire without a cartridge chambered. Remove the piece that carries the firing pin ... bolt, slide, whatever you want to call it ... and check for either an accumulation of crud, some kind of metal parts or the like like wire brush bristles that have fallen into the action, or damage which would keep the pin from traveling clear forward.
2) Is the gun misfiring with ammo .. either brand or batch .. that it was recently reliable with? Typically rimfires have to be headspaced by the thickness of the rim. If you've changed ammo, either brand / load / or even a new batch of something you've used before, you might have thinner rims so that the pin isn't impacting the rim with the same force because the cartridge is able to move forward a bit into the chamber.
3) Check the face of the "bolt" and the face of the barrel for crud that could be increasing headspace if it does not compress enough.
Tom
